What good resources are out there for learning Design patterns in C# and the .NET Framework?
Indeed there is:
Addison Wesley: .NET Patterns: Architecture, Design and Process
I don't know about books, or design patterns specifically for .NET, but Source Making has an excellent repository of design patterns, refactoring patterns, and anti-patterns that you might find useful.
Two of the most read books are the GoF book and Head First, you will find many references to them in very similar questions as yours.
Here is a site that uses both books as a start, but highlights the differences for C# :
C# 3.0 Design Patterns is ok http://www.amazon.com/3-0-Design-Patterns-Judith-Bishop/dp/059652773X/ref=sr_1_1?ie=UTF8&s=books&qid=1259063804&sr=8-1
It's also worth keeping an eye on the Patterns and Practices group on MSDN
Although the examples are in Java Martin Fowler's book Patterns of Enterprise Application Architecture is an excellent reference.
Also keep an eye on Martin Fowler's site http://www.martinfowler.com/